   (make-directed-graph (defined-concepts tbox)
                        (fn [A]
                          (free-symbols-in-expression
-                          (definition-expression (find-definition tbox A))))))
+                          (definition-expression
+                            (find-definition tbox A))))))
 
 (defn acyclic?
   "Returns true iff tbox is acyclic."

  "Substitutes for every defined concept name in tbox a new, globally
  unique, concept name and finally substitutes traget with its new name."
  [[tbox target]]
  (let [symbols     (defined-concepts tbox)]
    (when-not (some #(= target %) symbols)
      (illegal-argument "Target given to uniquify-ttp does not occur in the defined concepts of the given tbox."))
    (let [new-symbols (map-by-fn (fn [_] (gensym)) symbols)]
      [(make-tbox (tbox-language tbox)
                  (into {} (for [[sym sym-def] (tbox-definition-map tbox)]
                             [(new-symbols sym)
                              (make-dl-definition (new-symbols sym)
                                                  (substitute (definition-expression sym-def) new-symbols))])))
       (new-symbols target)])))

(defn uniquify-tbox

  [[tbox target]]
  (let [needed-targets (collect-targets tbox #{target} #{}),
	new-tbox       (make-tbox (tbox-language tbox)
                                  (select-keys (tbox-definition-map tbox)
                                               needed-targets))]
    [new-tbox target]))

(defn expand-ttp
